This application is a National Phase of PCT/EP2004/011637, filed Oct. 15, 2004, and claims the priority of German patent document DE 103 50 795.7, filed Oct. 29, 2003, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a directly injecting internal combustion engine with at least one cylinder which has a combustion space and in which a piston executes an oscillating movement.
A known internal combustion engine is described in U.S. patent publication No. 2002/0117146 A1. In this case, the fuel is injected at a relatively steep injection angle into the combustion space, and the piston recess is adapted at least partially to the injection angle.
In an internal combustion engine described in DE 196 49 052 A1, a special shape of the piston recess is likewise provided, in order to achieve an additional reduction in the pollutants emitted by the internal combustion engine.
When early homogenization is to be achieved within the combustion space of an operating internal combustion engine, in particular a diesel internal combustion engine, then injection time points of approximately 130 to 30° before the top dead center of the piston must be selected, since, at this time point, the combustion space pressure is still relatively low, so that the injected fuel can penetrate very deeply into the combustion space. In order to prevent the injection jet from impinging onto the cylinder wall or the liner, as steep an injection angle as possible at the injection nozzle should be selected, in order to ensure as long a free jet length as possible. This also requires the shape of the piston recess to be adapted to this injection, as is the case, for example, in US 2002/0117146 A1.
Since, however, it is not possible to operate the internal combustion engine with a homogeneous combustion process over its entire characteristic map, the piston recess must be designed both for homogeneous and for conventional mixture formation. This is not easily possible in known solutions.
An object of the present invention, therefore, is to provide a directly injecting internal combustion engine, in which the shape of the piston recess is configured such that the internal combustion engine can be operated by both a homogeneous and a conventional combustion process.
This object has been achieved, according to the invention providing that a surface of the piston recess which adjoins the elevation in the direction of the recess edge is connected to the elevation vi a radius in such a way that an injection jet impinging in this region and injected at the earliest possible time point is distributed both in the direction of the elevation and in the direction of the recess edge, and in that the surface adjoining the elevation in the direction of the recess edge has an extent in the direction of the recess edge such that an injection jet injected at the latest possible time point impinges onto the surface, the injection jet injected at the latest possible time point being distributed both in the direction of the elevation and in the direction of the recess edge.
The solution according to the invention ensures that the injection jet always impinges on the piston recess such that the injected fuel can be intermixed optimally with the air located in the combustion space, specifically independently of the time point of injection. Particularly the fact that an injection jet injected at the latest possible time point always impinges onto the surface adjoining the elevation ensures that the momentum of the impinging injection jet is not nullified, i.e., with the result from nullification that it could no longer be used optimally for mixture formation, which, in turn, would entail an increased formation of black smoke.
An internal combustion engine is thus afforded which can easily be operated by both a homogeneous and a conventional combustion process.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.